Entering its second decade, this program represents a systematic approach to the study of leukocyte chemotaxis with an emphasis on the biological functions of C5-related chemotactic peptides. Fragmentation products from 14C-C5 will be defined by physical-chemical parameters using convertases from a variety of sources. We will also investigate the nature of the inactivation products from C5a produced by the chemotactic factor inactivator. The other thrust of this study is to determine the pathogenesis of immune complex-induced tissue injury. An in vitro protease assay will be employed using both solid phase and fluid phase systems. Rat leukocytic proteases will be defined according to susceptibility to inhibitors which will then be used in conjunction with superoxide dimutase to determine if in vitro substrate hydrolysis and in vivo tissue injury can be averted by these inhibitors present alone or in combination.